Known field devices for automation engineering are designed to communicate with a higher-level device using a fieldbus protocol in order to perform an automation engineering task. For this purpose, these field devices have an interface for connecting to the fieldbus during, and for the purpose of, the intended use. In the simplest implementation, the HART protocol is used here for field communication.
In addition, the field device can be equipped with an additional interface for connecting to an operating device. This operating device is connected to the field device for configuration, commissioning, maintenance or updating firmware. For complex operating procedures, a personal computer has proved particularly useful as the operating device, in particular in its mobile form as a laptop or notebook. Field devices that can be operated in such a way are accordingly equipped with a UART-compatible standard interface for direct connection to the personal computer.
The disadvantage is that the UART standard interface supports only low data transfer rates and its operation is linked to interrupt requests (IRQ). Furthermore, modern personal computers tend not to have UART standard interfaces any more, so that instead of this, it is necessary to resort to additional equipment in the form of interface converters for converting the UART interface on the field device into the interface on the personal computer, usually USB. When using such interface converters, it has been found that timing problems hampering communication arise as a result of design differences between the converted interfaces.